Typically, components on a circuit board, such as microprocessors including CPU's and memory modules, or such as other integrated circuits typically found on a circuit board, including chipsets, graphics cards, along with hard drives generate heat. The heat generated by such components must be dissipated in order to ensure proper functioning of the components. Typically, heat sinks are used on these components to increase the surface area available for heat dissipation. Sometimes, the heat sinks are coupled with fans to speed up heat exchange.
In the case of multi-core server CPU's, a typical core region on a circuit board may be about 12 inches wide and about 7 inches long. As seen in FIG. 1, a portion of a typical motherboard or circuit board 100 is shown including a board substrate 102. The shown portion may include other components thereon, such as, for example, sockets 104. The shown portion further includes a multi-core server CPU region 105, which constitutes a heat generating arrangement 106 including a first CPU 108, a second CPU 110, and memory modules in the form of a first DRAM 112 and a second DRAM 114. Typically, the prior art places a heat sink, such as, in the shown example, a first heat sink 116 at a first half of the heat generating arrangement 106, and a second heat sink 118 at a second half of the heat generating arrangement 106. The heat sinks are shown in broken lines, and the border therebetween is also shown by way of broken lines in bold-face. Each heat sink 116/118 takes up about one half of the top surface of the heat generating arrangement 106, the heat sinks 116 and 118 being disposed in series with respect to one another (i.e.: an outlet of heat sink 116 corresponds to an inlet of heat sink 118). The portion of the circuit board 100 also includes an axial fan, such as axial rotary fan 120 disposed at an inlet of heat sink 116 and adapted to draw air therein, and to blow air into the heat sinks 116 and 118 to cool the heat generating arrangement 106 including the shown multi-core server CPU.
As can be seen from FIG. 1, CPU 110 is disadvantageously subjected to significant pre-heating of its coolant air from DRAM 114 disposed at an upstream region thereof. In other words, by the time the coolant air flowing first in heat sink 116 reaches heat sink 118 disposed on CPU 110, it is already significantly heated by the DRAM 114, such as for example by about 10 degrees Celsius. As components sizes decrease, the configuration in FIG. 1 would be ineffective for ensuring adequate heat removal from the heat generating arrangement.
In addition, as silicon integration continues, DRAMS may be integrated into CPU's. In such a case, a length dimension L of the heat sinks 116 and 118 may be cut by about a half, although their widths may remain substantially unchanged, while the heat generated per surface area of the CPU's would increase at least as a result of the DRAM integration. In such a case, the cooling system shown in FIG. 1, including the axial fan 120 and heat sinks 116 and 118 disposed in series would be far from adequate in dissipating the heat from the CPU's and integrated DRAMs.
The prior art fails to provide a cooling arrangement for cooling heat generating arrangements on a circuit board, such as heat generating arrangements including CPU's and DRAM's of decreasing sizes, and such as heat generating arrangements including CPU's having DRAM's or other memory modules integrated therein.
For simplicity and clarity of illustration, elements in the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Where considered appropriate, reference numerals have been repeated among the drawings to indicate corresponding or analogous elements.